RecruitingBehavioural interventionBiomarkers for ExerciseThe overarching objective is to examine the brain-based biological mechanistic pathway by which exercise exerts anxiolytic effects. The investigators will measure brain-derived markers of mitochondrial metabolism (acetyl-L-carnitine \[LAC\]) and inflammation (interleukin-6 \[IL-6\]) using innovative technology to isolate neuronal exosomes.